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United States Patent |
5,295,979
|
DeLaurentis
,   et al.
|
March 22, 1994
|
Urinary catheter and system
Abstract
A urinary catheter and system includes a catheter with a drain lumen which
is coated with oligodynamic metal and preferably arranged with a coating
of a more noble metal for creating an iontophoretic galvanic couple, which
drives antimicrobial ions into solution. The exterior of the catheter is
also coated in a similar manner to inhibit microbes migrating toward the
bladder along the outer surface of the catheter. The system includes a
flow rate control device which may be a one-way valve, a filter or both. A
collection bag is coupled to the control device. The interconnecting
hoses, the flow rate control device(s) and the collection bag are also
coated on the interior with oligodynamic metal, preferably silver, and
also with a more noble metal, preferably platinum.
Inventors:
|
DeLaurentis; Mark (Ocean Springs, MS);
Pourrezaei; Kambiz (Dresher, PA);
Boxman; Raymond L. (Herzliya, IL);
Beard; Richard B. (Atco, NJ)
|
Assignee:
|
P & D Medical Coatings, Inc. (Dresher, PA)
|
Appl. No.:
|
859062 |
Filed:
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March 27, 1992 |
Current U.S. Class: |
604/265; 604/328 |
Intern'l Class: |
A61M 005/32; A61M 025/00 |
Field of Search: |
604/93,264,265,280,327,328
|
References Cited
U.S. Patent Documents
2900979 | Aug., 1959 | Bishop | 604/327.
|
4232677 | Nov., 1980 | Leibinsohn | 604/265.
|
4677143 | Jun., 1987 | Laurin et al. | 604/265.
|
4840625 | Jun., 1989 | Bell | 604/349.
|
4886505 | Dec., 1989 | Haynes et al. | 604/265.
|
4933178 | Jun., 1990 | Capelli | 604/265.
|
5057094 | Oct., 1991 | Abbey | 604/327.
|
Primary Examiner: Shay; Randy C.
Attorney, Agent or Firm: Meise; William H.
Claims
What is claimed is:
1. A catheter defining inner and outer surfaces and distal and proximal
ends, said catheter comprising:
a smooth, flat continuous layer of a first metal extending over at least
one of said inner and outer surfaces, said continuous layer of first metal
extending from a point on said catheter to said distal end, said layer
underlying a discontinuous smooth, flat layer of a second metal,
dissimilar to said first metal, to thereby form contiguous exposed flat
patches of said first and second dissimilar metals.
2. A catheter according to claim 1 wherein said continuous layer of first
metal extends over both of said inner and outer surfaces.
3. A catheter according to claim 1, wherein said first metal is an
oligodynamic metal.
4. A catheter according to claim 3, wherein said second metal is more noble
than said oligodynamic metal.
5. A catheter according to claim 1 wherein said catheter defines a
longitudinal axis, and said patches are in the shape of coaxial annular
rings.
6. A catheter according to claim 1 wherein said patches are in the shape of
dots.
7. A catheter according to claim 1, wherein said patches are dimensioned so
that at least portions of three mutually adjacent patches can occupy a
region which, when said catheter is in use, lies within a urethra.
8. A catheter according to claim 1, further including a flow restriction
device coupled to the proximal end of said catheter, and a container
coupled to the end of said flow restriction device remote from said
catheter.
9. A catheter according to claim 8, wherein at least one of said flow
restriction device and said container include interior surfaces with
exposed dissimilar metals.
10. A catheter according to claim 9, wherein said container is fabricated
from a translucent or transparent polymer material, and said dissimilar
metals form a coating on a first portion of said interior surfaces of said
container, whereby a second portion of said translucent or transparent
polymer material forms a window for viewing the contents of said
container.
11. A catheter according to claim 9 wherein at least one of said dissimilar
metals coats a portion of said interior surface of said container in a
pattern comprising scale markings indicative of the volume of liquid
contained in the container when the liquid level is at a scale marking.
12. A catheter according to claim 9, wherein said dissimilar metals
associated with said container include an oligodynamic metal and a metal
more noble than said oligodynamic metal.
13. A catheter according to claim 9 wherein both said flow restriction
device and said container include interior surfaces with exposed
dissimilar metals.
14. A catheter according to claim 13, wherein said dissimilar metals
associated with said flow restriction device include an oligodynamic metal
and a metal more noble than said oligodynamic metal.
15. A catheter according to claim 8, wherein said flow restriction device
includes a filter, including filter elements of mutually dissimilar
metals.
16. A catheter according to claim 15, wherein said dissimilar metals
associated with said filter include an oligodynamic metal and a metal more
noble than said oligodynamic metal.
17. A catheter according to claim 8, wherein said flow restriction device
includes a one-way valve, which one-way valve includes interior surfaces
with exposed dissimilar metals.
18. A urinary catheter arrangement, comprising:
a catheter including a distal end, a proximal end, and inner and outer
surfaces, said catheter including a continuous layer of a first metal
extending over at least one of said inner and outer surfaces, said
continuous layer of first metal extending from a point on said catheter to
said distal end, said laxer of first metal underlying a discontinuous
layer of a second, dissimilar metal to thereby define contiguous exposed
patches of said first and second dissimilar metals;
a flow restriction device including an input port and an output port, the
exposed interior surfaces of which flow restriction device include an
oligodynamic metal;
a container including at least an input port, the exposed interior surfaces
of which container include an oligodynamic metal;
first flow coupling means coupled to said proximal end of said catheter and
to said input port of said flow restriction device for allowing flow
therebetween, said first flow coupling means including exposed interior
surfaces of oligodynamic metal; and
second flow coupling means coupled to said output port of said flow
restriction device and to said input port of said container for allowing
flow therebetween, said second flow coupling means including exposed
interior surfaces of oligodynamic metal.
19. A catheter according to claim 18, wherein at least one of said flow
restriction device and said container include interior surfaces with
exposed dissimilar metals, one of which is said oligodynamic metal.
20. A catheter according to claim 19, wherein the other one of said
dissimilar metals is a metal more noble than said oligodynamic metal.
21. A catheter according to claim 19, wherein both said flow restriction
device and said container include interior surfaces with exposed
dissimilar metals.
22. A catheter according to claim 21, wherein said dissimilar metals
associated with both said flow restriction device and said container
include said oligodynamic metal and a metal more noble than said
oligodynamic metal.
23. A catheter according to claim 18, wherein said flow restriction device
includes a filter, including filter elements of mutually dissimilar
metals.
24. A catheter according to claim 18, wherein said flow restriction device
includes a one-way valve, which one-way valve includes interior surfaces
with exposed dissimilar metals.
25. A catheter according to claim 24, wherein said dissimilar metals
associated with said one-way valve include an oligodynamic metal and a
metal more noble than said oligodynamic metal.
26. A urine collection container arrangement, comprising:
a container including deformable walls defining inner and outer surfaces,
and also including input and drain orifices;
a layer of a first metal extending over a portion of said inner surface of
said container;
a layer of a second metal, dissimilar to said first metal, extending over a
portion of said layer of a first metal on said inner surface of said
container, whereby said second metal is exposed to the inside of said
container, and said first metal is exposed in those regions not covered by
said second metal said first and second layers of metal being in physical
and electrical contact.
27. A container according to claim 26, wherein said first metal is an
oligodynamic metal.
28. A container according to claim 27, wherein said second metal is more
noble than said oligodynamic metal.
29. A container according to claim 26, wherein said deformable walls of
said container are fabricated from a translucent or transparent polymer
material, and said dissimilar metals together form a coating on a first
portion of said interior surfaces of said container, whereby a second
portion of said translucent or transparent polymer material forms a window
for viewing the contents of said container.
30. A container according to claim 29 wherein at least one of said
dissimilar metals coats a portion of said second portion of said interior
surfaces of said container in a pattern comprising scale markings
indicative of the volume of liquid contained in the container when the
liquid level is at a scale marking.
31. A container arrangement according to claim 26, further including a
catheter defining inner and outer surfaces and distal and proximal ends,
said catheter comprising:
a continuous layer of metal extending over at least one of said inner and
outer surfaces, said continuous layer of metal extending from a point on
said catheter to said distal end, said layer containing contiguous exposed
flat patches, each of said exposed flat patches including at least one of
first and second dissimilar metals.
32. An arrangement according to claim 31, wherein said continuous layer of
metal extends over both of said inner and outer surfaces.
33. An arrangement according to claim 32, wherein said first metal is an
oligodynamic metal.
34. An arrangement according to claim 33, wherein said second metal is more
noble than said oligodynamic metal.
35. An arrangement according to claim 31, wherein said patches are in the
shape of annular rings.
36. An arrangement according to claim 31 wherein said patches are in the
shape of dots.
37. An arrangement according to claim 31, wherein said patches are
dimensioned so that at least portions of three mutually adjacent patches
can occupy a region which, when said catheter is in use, lies within a
urethra.
38. An arrangement according to claim 31, further including a flow
restriction device coupled between said the proximal end of said catheter
and said input port of said container.
39. An arrangement according to claim 38, wherein said flow restriction
device includes interior surfaces with exposed dissimilar metals.
40. An arrangement according to claim 39, wherein said dissimilar metals
associated with said flow restriction device include an oligodynamic metal
and a metal more noble than said oligodynamic metal.
41. An arrangement according to claim 38, wherein said flow restriction
device includes a filter, including filter elements of mutually dissimilar
metals.
42. An arrangement according to claim 38, wherein said flow restriction
device includes a one-way valve, which one-way valve includes interior
surfaces with exposed dissimilar metals.
Description
BACKGROUND OF THE INVENTION
This invention relates to urinary catheters and catheter systems generally,
and more specifically to such catheters and other devices which are coated
with metal to reduce microbial infection.
Four million urinary catheters are used yearly in the United States, and
about 40 percent of patients develop uninary tract infections due to the
use of the catheter. About 3.2 percent of the total number develop
bacteriaemia (bacteria in the blood). Ten to twenty thousand people die
each year, and about one billion dollars are expended to manage the
complications arising from the use of urinary catheters and drainage
systems. Clearly, any means which helps to reduce such infections may have
a significant effect on the overall cost of medical services.
U.S. Pat. No. 3,598,127, issued Aug. 10, 1971 to Wepsic describes a
catheter in which V-shaped grooves or chambers are provided, which contain
antibacterial agents which diffuse through a permeable outer coating.
Other patents such as U.S. Pat. No. 4,612,337, issued Sep. 16, 1986 to
Fox, Jr. et al. describe various schemes for attaching or bonding
antimicrobial agents to catheter materials. In general, such antimicrobial
agents have a short half-life, and the microbes develop resistance to the
agent.
U.S. Pat. No. 4,054,139, issued Oct. 18, 1977 to Crossley describes a
catheter which embeds particles of "oligodynamic" (effective in small
quantities) metals in a plastic matrix on the inner and outer surfaces of
the catheter, to thereby inhibit microbial action. The matrix covers most
of the surface of those metal particles and may envelop other particles
completely. This arrangement, when used in a blood vessel, may produce an
effect in preventing actual colonization of the surface by microbes, but
may not be sufficient to kill or inhibit microbes migrating along the
space between the exterior of the catheter and the skin, because of
insufficient oligodynamic ion density, even though the space between the
outside of the catheter and the skin which is available for migration of
microbes is very small. However, the relatively large lumen required for
use as a urinary catheter renders an arrangement such as that of Crossley
essentially ineffective, for reasons described below.
U.S. Pat. No. 4,411,648, issued Oct. 25, 1983 in the name of Davis et al.
describes an arrangement which uses an external voltage source to drive
ions from a metal wire into fluid in the lumen of a urinary catheter. The
ions then diffuse into the bladder. No attempt is made to prevent bacteria
from moving along the outside of the catheter toward the bladder. The
Davis et al. arrangement acts on bacteria or microbes moving in reflux
from the exterior through the lumen, and also on those which are exiting
from the bladder through the lumen.
U.S. Pat. No. 4,569,673, issued Feb. 11, 1986 in the name of Tesi, shows a
pair of metal rings affixed on the exterior of a urinary catheter, with
the rings connected to an external power source, for reducing microbial
migration along the exterior of the catheter. Contamination through the
lumen, as for example due to reflux, is not taken into account, nor is the
possibility that, if microbes enter the bladder, they can colonize the
exterior of the catheter at locations more distal than the rings.
All of the above patents describe devices which have metallic surfaces
which are hydrophilic, and which confer protection against encrustation by
proteins and minerals. Plastics are generally hydrophobic, thereby tending
to increase the adhesion of bacteria and proteins.
U.S. Pat. No. 4,923,450 to Maeda, et al. describes a polymeric catheter
into which silver-containing zeolite is impregnated as an antimicrobial.
However, impregnation with zeolite decreases the tensile strength of the
catheter.
A copending application entitled "Metallic-Surface Antimicrobial,
Antithrombogenic Devices", filed concurrently herewith in the name of
DeLaurentis et al., describes catheters, artificial blood vessel, valves
or stents which are made from a combination of dissimilar metals which
provide both antimicrobial and antithrombogenic properties. A catheter
according to an aspect of the invention described in the DeLaurentis et
al. application provides a conduit for access between a blood vessel or
vas and the exterior of the body. The catheter includes a flexible tube
which defines at least inner and outer surfaces. A layer or coating of a
first metal (a metallization), supported by one or both of the inner or
outer surfaces of the catheter, extends from near the point of entry into
the vas to the distal end of the catheter. A coating of a second metal,
dissimilar from the first metal, is supported by the same one of the inner
or outer surfaces that supports the coating of the first metal. The
coating of the second metal is contiguous with, and in galvanic contact
with the coating of the first metal, thereby forming an iontophoretic
(ion-pumping) galvanic couple. The second metal coating extends proximally
from about the point of entry of the catheter into the vas to a location
outside the body. Thus, the two metals forming the couple are exposed in
different regions, and the antithrombogenic and antimicrobial properties
occur in different regions. In another embodiment of the DeLaurentis et
al. invention, the inside of the catheter is coated with two galvanically
connected dissimilar metals, and the junction therebetween is located at a
point sufficiently remote from the distal end so that it is ordinarily not
reached by blood. The two dissimilar metals may include an oligodynamic
metal such as silver and a more noble metal such as platinum. Stents,
valves and artificial blood vessels as described by DeLaurentis et al.
similarly include a junction of dissimilar metals, one of which may be
oligodynamic metal and the other a more noble metal. In particular, the
less noble or oligodynamic metal is located on that surface or surfaces of
the device which, when in use, are adjacent to solid body tissue, while in
all cases the more noble metal is adjacent the principal path for blood
flow for thereby reducing clot formation.
SUMMARY OF THE INVENTION
A urinary catheter according to the invention is coated on both the
interior (the lumen) and the exterior with a layer of exposed metals
selected to provide iontophoretic (ion-pumping) action by which
oligodynamic metal ions are driven into solution for inhibiting microbial
activity at locations adjacent to the exterior of the catheter, so as to
inhibit the migration of microbes into the urethra and bladder along the
exterior, and a similar coating along the interior of the lumen inhibits
microbes passing therethrough from the bladder. A urinary catheter system
according to the invention uses the abovedescribed catheter in conjunction
with a reflux reduction device such as a one-way valve or a flow rate
controller, a collection receptacle and interconnecting tubes, some or all
of which are made from or coated with metals for inhibiting microbial
activity.
DESCRIPTION OF THE DRAWING
FIG. 1 is an overall view of a simplified urinary catheter system according
to the invention, including a catheter, reflux reducing device, and
collection receptacle or bag;
FIG. 2a is a cross-sectional view of a portion of the urinary catheter of
FIG. 1, illustrating metallized surfaces, FIG. 2b is a perspective or
isometric view of the exterior surface of the catheter of FIG. 2a, and
FIG. 2c is a cross-section of a catheter with another metallization
pattern;
FIG. 3 illustrates a portion of a catheter tube, partially cut away to show
the presence of metal wool within the lumen;
FIG. 4a is a simplified side elevation view, partially cut away to reveal
interior details, of a flow rate control device according to the
invention, in the form of a filter, and FIG. 4b is a cross-section of a
hollow glass sphere which may be used within the filter of FIG. 4a;
FIG. 5a is a simplified side cross-sectional view of a one-way valve which
may be used with, or instead of, the filter of FIG. 4, and FIG. 5b is an
end view of the control flaps thereof;
FIG. 6 is a simplified side cross-sectional view of a modification of the
one-way valve of FIGS. 5a and 5b, modified by the addition of stiffened
flap ends;
FIG. 7a is a simplified view of a collection receptacle according to the
invention in a partially completed form, illustrating the interior
metallization pattern, and FIG. 7b illustrates the receptacle after
folding and sealing.
DESCRIPTION OF THE INVENTION
Experimentation with nutrient broths, which is considered a worst-case
condition, has revealed that inhibition of microbes requires about 25 to
50 square millimeters (mm) of silver surface per milliliter (ml) of broth
when that silver surface is not associated with a galvanic couple
providing iontophoretic action, and about half that amount of surface in
the presence of a galvanic couple. Simple geometric considerations
therefore limit the maximum diameter of the lumen of a catheter with a
simple silver coating to about 0.2 mm, and about 0.3 mm in the presence of
a couple. Such lumen diameters are inadequate for the flow rates which are
expected in urinary systems, especially at the time of initial
catheterization, when the flow rates may be high. A larger lumen must be
provided. The larger lumen, however, allows reflux of collected urine from
the collection receptacle or bag toward the bladder in the not uncommon
event that the collection receptacle is tilted while raised higher than
the patient. If the collected urine were sterile, the reflux would not
have injurious consequences. However, collected fluids may remain in the
collection receptacle for days, with some of the material being removed
periodically to prevent overfilling. The collection receptacle is at room
temperature. While urine is not an ideal medium for microbial growth, the
temperature and long growth interval conditions may allow colonization of
the interior of the collection receptacle and substantial microbial
densities in the fluid, which make reflux a serious matter. A catheter
system according to an aspect of the invention inhibits the migration of
microbes along the exterior of the catheter into the urethra and bladder,
and also inhibits microbes flowing through the catheter system and
reposing in the collection receptacle. Further, in another embodiment of
the invention, reflux is impeded by a device for restricting flow in one
direction (a valve) or by a bilateral flow rate restriction device.
In FIG. 1, a catheter system 10 includes an elongated catheter 12 defining
a distal end 14 and a proximal end designated generally as 16. Catheter 12
includes a retention balloon 18, illustrated in its deflated state, which
communicates by way of an inflation lumen (not illustrated in FIG. 1) with
an inflation connector 20. A main lumen (not illustrated in FIG. 1)
extends from a distal aperture 22 to proximal end 16 of the catheter, at
which it connects to a drain tube 24. Drain tube 24 extends to a reflux
avoidance device designated 30, which is described in more detail below. A
further tube 32 extends from reflux avoidance device 30 to a collection
container in the form of a closed bag 40, which includes a handle or strap
42 for hanging, and also includes a drain tube 44 and drain tube shutoff
clamp 46. A transparent window 48 in the side of container 40 is
associated with a scale (not illustrated in FIG. 1).
FIG. 2a is a cross-sectional view of catheter 12 of FIG. 1, illustrating a
body 210 made from a polymer such as tetrafluoroethylene, defining a
balloon inflation lumen 212 and a main drainage lumen 214. Inflation lumen
212 communicates with balloon 18 and with inflation port or connection 16
of FIG. 1, and drain lumen 214 communicates with distal aperture 22 and
with drain tube 24 of FIG. 1. As illustrated in FIG. 2, the exterior
surface of catheter 12 is covered with exposed metallic coatings. A
continuous layer 216 of a first metal is covered with mutually separated
dots or spots 218 of a second metal. The exterior surfaces of those
portions of layer 216 which do not lie under dots 218 are exposed, and the
surfaces of dots 218 are also exposed. FIG. 2b is a perspective or
isometric view of a possible shape for such dots or spots, but the exact
shape is not of great significance. In accordance with an aspect of the
invention, the second metal is an oligodynamic metal such as silver, while
the partially exposed underlying metal layer is a more noble metal such as
platinum. This combination of metals sets up a galvanic couple which
promotes iontophoresis, or the generation of ions. In the arrangement as
described, silver ions are generated at dots 218 when the catheter is in
place, since the surrounding urine and mucous fluids act as an electrolyte
through which minute amounts of electrical current may flow. These silver
ions go into solution, and, at a sufficient density, inhibit microbial
growth.
The surfaces of retention balloon 18 of FIG. 1 are also covered with
exposed metal surfaces as described above. Most catheter balloon materials
are not very elastic, and the balloons are might more properly termed
"bags", but the "balloon" terminology is well established. The retention
balloon, the outer surface of the catheter in the distal region, and the
lumen in the distal region, and drain aperture 22, preferably are all
coated with interconnected exposed metal, so that no uncoated regions
remain where microbial colonization could occur.
As mentioned in copending patent application Ser. No. 07/859,063 entitled
"Method for Fabrication of Metallized Catheters", filed Mar. 27, 1992 in
the name of Pourrezaei et al., the corrosion of exposed silver in a
galvanic couple such as that described in conjunction with FIGS. 2a and 2b
could, if the silver layer were the underlying exposed layer 216 and the
dots 218 were platinum, result in disconnection of the exposed silver from
the platinum dots, thereby reducing the amount of silver connected to the
galvanic couple, and reducing the activity of the device even though
exposed silver remains. The arrangement as illustrated in FIGS. 2a and 2b
allows the galvanic couple to operate until such time as the silver dots
are completely dissolved. An initial corrosion rate of about 1/2 micron
per week is expected, which rate decreases as the concentration of ions in
solution increases, so the overall corrosion rate should not exceed about
1/2 micron per week, and dots which are a few microns thick should be more
than enough for ordinary use.
As also indicated in the abovementioned Pourrezaei et al. application, the
adhesion of some metals to underlying polymers may not be adequate for
prolonged use in the presence of watery fluids, because the water tends to
migrate through pores and cracks in the metallic coatings to attack and
loosen the attachment to the base material. As therein described, an
improvement is achieved by applying a first or base coating of silver for
good adhesion, following which one or more additional layers may be
applied, with the outermost "incomplete" layer (corresponding to dots 218
of FIGS. 2a and 2b) being silver or other oligodynamic metal, and the
outermost "complete" layer (corresponding to partially exposed layer 216
of FIGS. 2a and 2b) being platinum or other metal more noble than the
oligodynamic layer. In FIG. 2a, layer 220 is an adhesion-enhancing silver
layer, which is completely covered by platinum layer 216. Additional
layers of silver, or of alternating layers of silver and platinum, or of
other metals, may be interposed between layers 216 and 220, for filling
pores and cracks.
The surface of drain lumen 214 of catheter 12 of FIG. 2a is coated with a
layer 230 of silver, which is connected at proximal and distal ends of the
lumen to a more noble metal, as by connection to exterior platinum layer
216. Thus, silver layer 230 is part of a galvanic couple, for
iontophoresis. Ideally, a pattern of silver dots is also applied over an
underlying platinum layer on the surface of the lumen, but the additional
plating steps may be a manufacturing effort which is not be justified by a
corresponding increase in the oligodynamic ion density. This is especially
true, considering that the desired ratio of silver surface to volume for
complete inhibition throughout the volume of the lumen cannot be achieved
for a lumen diameter greater than about 0.2 mm when the walls alone are
relied upon. The silver ion density near the lumen surface or walls may,
however, be sufficiently high to prevent colonization of the surface of
the lumen.
The catheter, and other devices described herein, may be made by
conventional methods, or by the improved methods described in the
abovementioned copending Pourrezaei et al patent application Catheters or
other devices according to an aspect of the invention described in the
aforementioned Pourrezaei et al. application include those in which plural
layers of metals are applied to the surfaces of the device, which tend to
close minuscule cracks or pores through which corrosion may attack the
underlying support structure. The catheter support may be made from TEFLON
(polytetrafluoroethylene) or from other materials. In some embodiments or
avatars, the initial layer of material is preferably silver, applied
following preparation steps which may include cleaning, drying and
etching. In some embodiments, succeeding layers of metal completely cover
the initial layer, and are also of silver. The succeeding layers are
deposited after deposition of the prior layer has ceased, and such
succeeding layers have unexpectedly been found to tend to reduce the
incidence of microscopic pores or cracks and to therefore be less prone to
delamination. The succeeding layers are preferably of mutually different
metals between layers. In a particular avatar, in which the exposed metals
are silver (or other oligodynamic metal) and platinum (or other more noble
metal), the exposed silver layer lies over a portion of the platinum
layer, to thereby prevent corrosion of the silver layer near the junction
of the metals from electrically disconnecting portions of the silver layer
from the platinum. Fabrication methods include deposition of successive
layers by means of sputtering a continuous run of catheter material in a
longitudinal array of cylindrical (or other) magnetrons or magnetron
sections or segments, in which each magnetron or section thereof applies
one layer of the coating over the coating applied by the preceding
magnetron or section of the array. The magnetrons or sections may be
energized and deenergized in a temporal pattern associated with the
progress of the catheter material through the array, to thereby cover or
expose particular layers at particular positions along the length of the
catheter material. In some embodiments of the invention, a first layer of
electrically conductive material is deposited by electroless methods,
following which additional layers may be applied by conventional
electrolytic deposition. An electroless application method may be used for
depositions in a lumen of a catheter. An electroless method according to
the Pourrezaei et al. invention includes preparation steps which may
include ultrasonically cleaning the surface with a solution of isopropyl
alcohol, then drying the surface with a stream of dry gas, and etching the
surface with a solution of sodium naphthalene in diethylene glycol
dimethyl ether, commercially available as CHEM-GRIP TREATING AGENT from
Norton Performance Plastics of Wayne, N.J. After the preparation steps,
the inner surface is acidified and neutralized by hydrochloric acid,
sensitized with a solution of SnCl.sub.2 /HCl, and rinsed. The actual
electroless plating is accomplished by a plating solution including
AgNO.sub.3, sodium dodecylbenzenesulfonate, and ammonia solution, with
acetic acid added for pH adjustment, together with a reducing solution of
N.sub.2 H.sub.4 :H.sub.2 O(hydrazine hydrate). Each of the above steps may
be separated from the next by rinsing and drying steps.
FIG. 2c is a cross-section of a portion of a catheter according to another
aspect of the invention, illustrating a polymer body 250, with a
continuous coating 252 of platinum on the exterior surface, and with
additional annular rings 254 of silver extending about the body.
Similarly, the drain lumen 256 has a continuous coating 258 of platinum,
over which rings 260 of silver are applied. The patterns are readily
accomplished by masking.
It is believed that, in order for the iontophoresis to be fully effective,
portions of at least three mutually adjacent patches or rings must reside
within the urethra. Thus, one ring or patch or silver, with at least a
portion of a platinum patch at the distal end and a portion of another
platinum patch at the proximal end lying within the urethra, would be
sufficient. Preferably, a large number of patches would reside therein.
In accordance with an aspect of the invention, the surface-to-volume ratio
is improved as illustrated in FIG. 3 by making the exposed surface 330 of
a lumen 214 of platinum, and by filling the lumen with silver wool 332.
The silver wool makes contact with the platinum walls of the lumen at
numerous points, thereby generating the desired galvanic action, and the
density of the silver fibers can be selected to provide the desired
surface-to-volume ratio. Naturally, the metal wool could also be made from
platinum, and the lumen walls from silver, or the wool could be an
intermixture of oligodynamic and more noble metal fibers. The preferred
arrangement includes lumen walls of exposed silver, together with metal
wool of intermixed silver- and platinum-surface fibers.
FIG. 4a is a side cross-section of a flow restricting device 300 which may
be used in place of device 30 of FIG. 1. In FIG. 4a, a drum-shaped
container includes input and output hose connectors 410 and 412,
respectively. The inner surface of container 300 is coated with exposed
silver, which coating may be of multiple layers, as mentioned. The
interior of device 300 is filled with a large number of small particles or
spheres 414, the exposed surfaces of which are an intermixture of silver
and platinum, retained in place by screens 416. The simplest arrangement
is to fill the interior with a mixture of silver and platinum powders,
thereby creating innumerable small passages, each with an effective
diameter less than 0.2 mm. Each such small passage alone has excessive
resistance to liquid flow, but the large number of such passages in
parallel, together with the large diameter of device 300, provide
sufficient flow. Material may be conserved by filling the interior of
device 300 with small glass spheres, some of which are coated with silver,
and others of which are coated with platinum. FIG. 4b is a cross-section
of such a sphere 414, illustrating an empty center 415 surrounded by a
glass bubble 418, the exterior surface of which is coated with a layer 420
of metal. In operation, device 300 provides a relatively high flow rate,
but also interposes a delay from the time that flow begins at one side
until it emerges from the other side. This delay allows the position of
the container to be readjusted before reflux flow reaches the patient. At
the same time, the high ion density within the small passages of the
device tends to inhibit microbes within the flow, and in ordinary use will
tend to increase the ion density within container 40, thereby tending to
minimize microbial growth therein.
In FIG. 5a, a one-way valve 500 which may be used instead of, or in
conjunction with, filter 300 of FIG. 4, includes a body 502 defining a
cylindrical center region 514. Within center region 514, a plurality of
thin, flexible control vanes or flaps 516a through 516h are attached at
one end to the wall of body 502 and extend, partially overlapping each
other, to the center. FIG. 5b is an axial view of the flaps, looking along
section lines 5b-5b of FIG. 5a. For flow from input port 510 toward output
port 512, each flap is supported essentially only at its attachment to
body 502, so each flap can deflect downward to allow flow. Retrograde flow
is impeded by the flaps, which are prevented from deflecting in the flow
direction by the support of adjacent flaps. In accordance with an aspect
of the invention, the interior walls of body 502, and each of the flaps
516, is coated with one or more metals, at least one of which is
oligodynamic. Except during heavy flows during initial catheterization,
the flow is a trickle which flows in a thin film over the interior
surfaces of the valve, and in which microbial inhibition will therefore
occur with a simple oligodynamic metal coating. To enhance activity, the
major surfaces of the flaps may be coated with silver, and the edges of
the flaps in the overlapping regions may be coated with platinum, to
provide an iontophoretic couple. The flaps are relatively narrow near the
center of the structure, as well as being thin and flexible. Consequently,
each flap, at a location most remote from its support by body 502, has
little structural strength, and even in a mutually supporting arrangement
may deflect in the event of a substantial reflux fluid pressure.
FIG. 6 is a simplified side cross-section of another one-way flow valve,
generally similar to that of FIG. 5a and 5b. In FIG. 6, body 602 supports
valve flaps 616 as described above, but the end of each valve flap 616 at
a location most remote from its support by body 502 is truncated, and a
more rigid flap portion 618 extends toward the center of the structure
from the point of truncation. Thus, the relatively weak tips of the flaps
are replaced by stronger, more rigid structures for added resistance to
reflux pressure.
FIG. 7a is a simplified view of an unfolded or partially manufactured
urinary catheter collection bag according to the invention, which may be
used in the arrangement of FIG. 1. The side of sheet 710 visible in FIG.
7a is the side which, after folding along fold line 702 and peripheral
sealing during fabrication, lies within the collection bag. In FIG. 7a, a
rectangular sheet 710 of transparent or translucent polymer includes an
outer margin region 712a and 712b, where no metallic coating is provided.
Region 712a is a region in which sealing takes place at a later step of
fabrication, and region 712b is a region which is later available as a
window, for ascertaining the level of the collected fluid. According to an
aspect of the invention, the main portion of the visible side of sheet 710
is coated with exposed metal. As described in more detail in the
abovementioned copending DeLaurentis et al. and Pourrezaei et al.
applications, the coating may constitute a layer 714 of a first metal
which extends over the entirety of the metallized region, over portions or
patches of which a second layer 716 of metal is applied, to result in
exposed portions of two metals. The preferred second exposed metal is an
oligodynamic metal such as silver, and the first metal is a more noble
metal such as platinum.
The metal pattern in FIG. 7a may be deposited with the aid of a first mask
for depositing the underlying layer of metal 714 over the entire surface
except for the outer margin regions 712a and 712b, followed by a second
mask which defines the second patches, and which prevents deposition of
the second metal layer 716 on the outer margin area. The first masking
operation may be dispensed with in conjunction with the deposition of
first metal layer 714, whereby the deposition takes place all the way to
the edge of the sheet, in which case sealing is accomplished by folding
over the edges, so that a portion of the uncoated "outer" surface forms an
effective margin, and those uncoated margin portions of the outer surface
may be sealed together. Sheet 710 of FIG. 7a may be made from a
thermoplastic material, which is masked and coated as described above.
Assuming that the marginal regions 712a and 712b, as illustrated in FIG.
7a, are not coated with metal, sheet 710 is folded along its fold line
702, and the input and output ports are then placed in position. Heat and
pressure are applied to sealing surface 712a, thereby sealing the edges of
the container, and also sealing the container to the input and output
ports. During sealing, some heat is also applied to region 712b while a
slight overpressure of air is applied to the ports, to allow plastic flow
in region 712b, which allows the volume of the completed receptacle to
increase. The input and drainage ports may be molded in known fashion with
an almond-shaped or tapered cross-section where they enter and seal to the
bag, and with round cross-section at the free ends, to thereby allow
coupling to standard connectors.
FIG. 7b is a view of the exterior of the collection receptacle of FIG. 7a
after folding, adding input and drainage ports, and sealing. As
illustrated, the central region 740 is opaque because of the application
of metallization layers 714 and 716 of FIG. 7a. A scale 750 may be printed
on the outside of the collection receptacle, or preferably the scale
markings are metallic coating applied to the interior as part of the same
step by which one of the first or second metal coatings 714, 716 is
applied, to thereby eliminate one manufacturing step.
In accordance with another aspect of the invention, all the interconnecting
hoses, such as hoses 24 and 32 of FIG. 1, are coated on the inside
surface, i.e. the surface of the drain lumen, with a layer of oligodynamic
metal such as silver, which is in communication with the coatings of the
adjacent device. Thus, a continuous metallic antimicrobial coating extends
through the drain lumen from the distal end of catheter 12 of FIG. 1,
through the catheter, hose 24, filter 30 of FIGS. 1 and 4a and or one-way
valve 500 of FIG. 5, and through hose 32 of FIG. 1, and into receptacle
40. This continuous coating preferably includes an oligodynamic metal, and
is preferably rendered more active by iontophoresis provided by a galvanic
couple. The most preferred arrangement includes the abovementioned
continuous coating through the drain lumen, together with a metallic
coating on the exterior surface of the catheter itself, as described in
conjunction with FIGS. 2a and 2b, to inhibit migration of microbes along
the outer surface of the catheter.
The metallic coatings of the various surfaces may be made by conventional
methods or by the methods described in the aforementioned Pourrezaei et
al. application. The dots, or other patterns on the exterior surface, may
be made by simple masking techniques. Patterns on the interior surfaces of
lumens may be made by electrodeposition from electrodes having the desired
pattern, as for example an interconnected pattern may be electrodeposited
by a metallic screen.
In order to avoid the possibility of introduction of microbes into the
interior of a hose, filter, valve or bag, the entire drain system,
including the catheter if desired, can be assembled at the factory and
sterilized after assembly by heat, radiation, or in any other fashion.
Since there is no need for opening the closed system prior to use, there
is no opportunity for ingress of microbes prior to catheterization such as
might occur if the system had to be assembled from separate elements and
hoses. The catheter system as described should remain free of active
microbe colonies longer than other systems, thereby reducing the
occurrences of infections with their complications, and also reducing the
need for additional, replacement catheter systems, and the risks involved
in recatheterization.
Other embodiments of the invention will be apparent to those skilled in the
art. In particular, a one-way valve such as that of FIG. 5 may be used
together with a flow rate reducing filter such as that of FIG. 4a. While
silver has been described as the exposed oligodynamic metal which is
corroded to produce microbe-inhibiting ions, other metals such as aluminum
are known to produce a like effect. When used for draining bile from the
bile ducts into the duodenum, a catheter coated in a manner such as that
described may retard blockage by inhibiting the microbial growth which
converts bile into an adhesive substance. While a tetrafluoroethylene
substrate material has been described, other polymeric materials such as
silicone may be used.
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